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Steroid Hormone Receptors

Endocrinology refers to the study of endocrine system; more specifically, it is the study of hormones, the receptors to which the hormones bind, the intracellular signaling cascade they invoke, and the diseases and conditions associated with them. It is a communication system comprising of endocrine glands and the hormones they produce. The hormones are released into the blood to guide processes such as metabolic activity, growth, sexual development, sleep-wake homeostasis, regulation of emotions, and others. The effect produced by the hormones might rest with a single organ or multiple organs throughout the body.
This article specifically focuses on the intricacies of the steroid hormone receptors, which are generally intracellular in nature and can be found at all three places namely nucleus, cytoplasm and the plasma membrane.

00:02
Let’s talk about steroid hormones please.
00:05
Now, steroid hormones,you want think of this as being a separate topiconly because its mechanism
is a little bit different.
00:10
It's quite interesting here.
00:11
You're going to like this.
00:12
Watch.
00:14
Let’s talk about steroid hormones,specifically adrenal cortex.
00:16
Are we there now?Before we get to the adrenal cortex,couple of things that you
want to keep in mindis when would you releaseor how would you releasesome of these hormones
from the adrenal cortex.
00:29
ACTH.
00:30
Coming from where?Anterior pituitary.
00:33
What’s the name of the releasing hormone?Corticotropin releasing hormone.
00:36
Good.
00:37
Now, ACTH is going to kick start the
synthesis of your adrenocortical hormones.
00:44
The next thing which you want to do
is give yourself an acronym,right?Give yourself an acronym
for the adrenal cortex.
00:50
GFR.
00:53
Remember, now with the adrenals,you want to divide it into
two separate structures.
00:58
What is that?The cortex and the medulla.
01:00
The cortex and the medulla.
01:02
The medulla is always
in the inner aspect;the cortex, obviously, outer.
01:05
The outer aspect of the adrenal
is known as adrenal cortex.
01:09
You will divide that into GF and R
if you haven't done so already.
01:13
The G stands for zona glomerulosa.
01:16
F stands for zona fasciculata.
01:18
R stands for zona reticularis.
F stands for zona fasciculata.
01:18
R stands for zona reticularis.
01:20
You might've heard of the phrase,the deeper I go, the sweeter it gets.
01:25
What am I referring to?The deeper you go,adrenal cortex,the zona reticularis,I am going to release sex hormones.
01:36
The glomerulosa, you’re releasing what?Aldosterone.
01:40
Mineralocorticoid.
01:44
From your fasciculata,what are you releasing?Glucocorticoid.
01:51
Deeper I go, sweeter it gets.
01:53
Reticularis, I am releasing androgens.
01:58
Where are the receptors?In general,whenever you deal with steroid hormones,these are true or false?Always, lipid soluble?True. Always lipid soluble.
02:14
So, no matter what,your steroid hormones will always
pass through the membrane.
02:18
The next question is,where are my receptors located?Is it the cytoplasm
or is it the nucleus?Here it’s the cytoplasm.
02:27
Welcome to adrenocortical hormones.
02:32
Mineralocorticoid,cortisol,androgen from adrenal cortex.
02:38
Receptor located where? In the cytoplasm.
02:42
Let’s take a look at
the other column.
02:44
Before we move on,it’s still steroid hormones.
02:48
We just said,steroid hormones will always
pass through the membrane.
02:52
Now, where are these receptors located?Look please.
02:56
Nucleus, nucleus, nucleus.
02:58
These include estrogen –oh, my goodness, estrogen.
03:02
We’ll talk about what estrogen quite a bit.
03:04
How important is that hormone?Quite.
03:08
Not just in a female,but then in a male tooand especially as we get
into our gonadal pathology.
but then in a male tooand especially as we get
into our gonadal pathology.
03:14
Thyroid hormone receptor.
03:16
Thyroid hormone.
03:17
Would you tell me what is the predominant
thyroid hormone that is released?By predominant,I mean greater concentration of your thyroid hormonebeing released in the anterior pituitary,by far, it's T4.
03:30
They’re not going to
ask you how much.
03:32
It could be maybe 20 to 1 ratio,15 to 1 ratio,whatever.
03:36
The point is you’re releasing excessive T4.
03:41
The active type of thyroid
hormone, of course, is T3.
03:45
We’ll talk about that in greater detail.
03:48
Vitamin D.
03:49
From henceforth,you want to think of
vitamin D as being a hormone.
03:54
Vitamin D, what does it do?Active type.
03:58
Where is active type of
vitamin D being synthesized?Go back to nephrology.
04:03
In your proximal convoluted tubule,what was the name of the
enzyme in the PCT in the –to activate your vitamin D?Good.
04:11
1α-hydroxylase.
04:13
What's that active form of vitamin D called?Do not ever forget that.
04:16
It's also called calcitriol.
04:19
Keep going.
04:20
What is the name of the hormonethat's responsible for stimulating
that enzyme in the PCT?It’s PTH.
04:26
All of that,as you know,is incredibly important.
04:29
Do not forget that.
04:30
Because if you’re going to renal failure,that enzyme known as 1α-hydroxylasecan never be stimulated by PTH.
04:36
Hence your patient with renal
failure will always be hypocalcemic.
04:40
And always have what kind of hyperparathyroidism?Secondary, secondary, secondary, secondary, secondary.
04:47
Then we have retinoic acid receptor.
04:51
Put these two together.
04:53
Vitamin D, vitamin A.
04:55
Vitamin D, vitamin A.
04:56
That’s retinoic acid, isn’t it?A type of vitamin A.
05:01
So, both of these vitamins,you want to think of as being a lipid soluble,passes through the membrane.
05:08
It works in the nucleus,so that it can bring about particular effects.
05:13
With vitamin D,let’s say that you go
into the GI and intestine.
05:17
It's going to work upon – work in the nucleus,so that you up-regulatewhat’s known as calcium-binding protein (CBP).
05:24
That calcium-binding protein obviouslyresponsible for reabsorption of calcium.
05:30
And in pathology,when you don't have
vitamin D for whatever reason,you are rendered as an adult osteomalacia.
05:38
And if it's a child, welcome to rickets, right?And then what about retinoic acid?Remember WBC pathology.
05:45
What was the translocation that we saw,with acute myelogenous leukemia type 3, M3,that up-regulates retinoic acid receptor?Good. 15, 17.
06:00
Well, how do you use this
to your advantage?Use the ATRA (all-trans retinoic acid).
06:05
Remember?If you don't,go back and take a look.
06:08
All of this is crucial.
06:09
Put things together.
06:11
It works upon retinoic acid receptor,so that it can do what?
It works upon retinoic acid receptor,so that it can do what?So that you can properly mature yourselves.
06:17
So, therefore,if a patient doesn't have vitamin A,that patient is rendered blind.
06:25
What kind?Colorblindness.
06:27
And if vitamin A isn't present,tell me about the conjunctiva.
06:32
It doesn't properly mature.
06:33
Welcome to keratoconjunctivitis.
06:36
Clear?Important.

About the Lecture

The lecture Steroid Hormone Receptors by Carlo Raj, MD is from the course Introduction to the Endocrine System.

Included Quiz Questions

Which of the following is a correct match of the steroid hormone receptor with it's corresponding region of the adrenal cortex?

Zona fasciculata — glucocorticoid receptor

Zona glomerulosa — glucocorticoid receptor

Zona fasciculata — mineralocorticoid receptor

Zona reticularis — mineralocorticoid receptor

Zona glomerulosa — androgen receptor

All steroid hormone receptors are located in the nucleus EXCEPT which of the following?

Androgen receptor

Estrogen receptor

Vitamin D receptor

Thyroid hormone receptor

Retinoic acid receptor

Which of the following hormones is paired with the correct active form?

Vitamin D — calcitriol

Thyroid hormone — T4

Vitamin D — PDH

Estrogen — prolactin

Thyroid hormone — retinoic acid

A patient has color blindness. Which steroid hormone receptor may be involved?

Retinoic acid receptor

Vitamin D receptor

Androgen receptor

Mineralocorticoid receptor

Glucocorticoid receptor

Which of the hormones produced in the anterior pituitary signals the adrenal glands to release its hormones?

ACTH

TSH

FSH

LH

GH

Author of lecture Steroid Hormone Receptors

Carlo Raj, MD

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